Data from rectal cancer patients who underwent TaTME assisted by laparoscopy between October 2018 and March 2022 at the First Affiliated Hospital of Fujian medical university were used to compile the database. The patients in this study met the following inclusion criteria: 1) malignant tumors were confirmed by computed tomography, magnetic resonance imaging, or pathological diagnosis; 2) clinical records and follow-up information with imaging and physical exam were available. The subsequent exclusion criteria were identified: 1) patients under the age of 18; 2) patients with previous abdominal or pelvic surgery history; 3) patients with multiple primary cancers; 4) patients allergic to ICG or iodine, along with those who were currently receiving iodine dyes or medications likely ICG; 5) conversion to open surgery; 6) emergent cases.

Patients were separated into the ICG and non-ICG groups. Whether patients underwent ICG or clinical assessment evaluation for colonic vascular perfusion was at the discretion of the multidisciplinary team (MDT) and the patient’s intent. The TaTME was performed on each patient with the same surgical group. Patients’ demographics (age, sex, body mass index [BMI], albumin [ALB], comorbidities [including diabetes, hypertension, cardiovascular disease, smoking history, cirrhosis, and steroid use at the time of surgery], and American Society of Anesthesiologists [ASA] scores), tumor features (TNM staging, tumor diameter, distance from the anal verge, and neoadjuvant CRT), operative characteristics (ligation level of inferior mesenteric artery [IMA], anastomosis level from the anal verge, extraction site, operative time, intraoperative blood loss, prophylactic stoma, anastomotic perfusion score, and surgical plan changing including modification of the proximal colonic transection or further surgical operations), and postoperative outcomes [postoperative hospital stay, AL, abdominal/pelvic abscess, surgical reinterventions, ileus, bleeding, acute urinary retention, wound infection and hospital readmission, and other complications with a Clavien–Dindo classification score of grade II or higher occurring during the first 30 days following surgery (30)] were documented in a case report form (CRF).

TaTME was performed in accordance with previous studies (31). Real-time proximal colonic vascular perfusion assessment was conducted at our center with the laparoscopic NIR camera system provided by Karl Storz (D-Light P; Tuttlingen, Germany) and the Stryker Corporation (1588 AIM Platform, Michigan, USA) just before and after performing the anastomosis by evaluating the mucosa through transanal visualization. Before injecting ICG, the surgeon marked the planned transection colonic line with electrocautery under white light for the initial evaluation. This was performed after the bowel was mobilized, the rectum was transected, the inferior mesenteric vessels were transected, the splenic flexure was mobilized (if it was deemed necessary), and the mesocolon was sectioned, once the specimen had been transabdominally or transanally externalized and before the anastomosis creation. In accordance with the guidance protocol, a bolus of ICG of 0.25 mg/kg was administered intravenously through a peripheral line by the anesthesiology team. The international normalized ratio (INR) was utilized to evaluate colonic perfusion, and the boundary line between the perfused and non-perfused tissue was marked and compared to the planned initial point of the transection. The anastomosis was subsequently created and then another bolus of ICG to evaluate anastomotic perfusion endoluminally (32). The NIR was administered by the transanal device repositioned in the anus. Through the transanal device placed again in the anus, the NIR was introduced. If the surgeon considered that it was required, the patient could receive an ICG third dose (for instance, following an additional surgical procedure including the splenic flexure mobilization if there is too much tension at the mesenteric or anastomotic site, the third injection would be taken).

Proximal colon/anastomotic vascular perfusion was assessed by using an anastomotic perfusion scoring system according to D.A. Sherwinter et al. (33): for clinical assessment in the non-ICG group, dusky appearance was assigned 1 point; patchy appearance was assigned 2 points; pink appearance without pulsatility or bleeding cut edges was assigned 3 points; pink appearance, mesenteric vasculature pulsatility, and bleeding cut edges, but with clinical concern over viability, were assigned 4 points; pink bowel appearance, mesenteric vasculature pulsatility, and bleeding from the cut edge of bowel were assigned 5 points. For fluorescence assessment (30–60 s after ICG injection) in the ICG group, no uptake was marked as 1 point, patchy fluorescence was marked as 2 points, significantly hypofluorescent but homogeneous was marked as 3 points, somewhat hypofluorescent compared to other segments was marked as 4 points, and hypofluorescent to all other segments was marked as 5 points. For both groups, a score of 4 to 5 was considered adequate perfusion for anatomy creation, and 1–2 points indicated poor perfusion, which needed modification of the proximal colonic transection. Whether interventions were needed for patients with 3 points depends on the discretion of MDT and the patient’s condition and intent (32, 33).

AL was defined as a defect of the intestinal wall integrity at the anastomosis site (including suture and staple lines of neorectal reservoirs) that permitted connection between intra- and extraluminal compartments regarding the definition and grading of anastomotic leakage of the International Study Group of Rectal Cancer (34), as confirmed by rectal contrast radiologic extravasation evidence or digital rectal examination within 30 days after the operation. According to the impact on clinical management, the severity of AL should be graded. AL of grade A required no modification in the management of patients, AL of grade B required active therapeutic intervention but is manageable without re-laparotomy, and AL of grade C required re-laparotomy (34).

Nearest neighbor propensity score matching (PSM) extracted 1:1 matched pairs of subjects from the non-ICG group or the ICG group based on patient features involving age, sex, BMI, ALB, comorbidities, ASA scores, and tumor features involving tumor diameter, distance from the anal verge, TNM stage, and neoadjuvant CRT. Continuous variables are represented by median (minimum–maximum) or mean ± standard deviations (SDs). To analyze differences in categorical variables, the chi-squared or Fisher’s exact test was applied. The Wilcoxon rank-sum test was utilized to compare continuous variables between groups. p < 0.05 indicated that differences between the two groups were statistically significant. R 3.3.0 was utilized to conduct analyses.

This study was authorized by the Ethics Review Committee of the First Affiliated Hospital of Fujian Medical University [Approval No. (2018)068], and all patients provided written informed permission. All procedures were conducted in conformity with the principles of the Declaration of Helsinki.

This study included a total of 370 individuals who underwent TaTME at the First Affiliated Hospital of Fujian medical university. Table 1 outlines the patient and tumor features that were present before PSM (227 in the non-ICG group and 143 in the ICG group). Before PSM, the ICG group was older and had a shorter distance from the anal verge than the non-ICG group. Following PSM, 143 patients from the non-ICG group and 143 patients from the ICG group were ultimately enrolled in this study. There was no significant difference between the two groups concerning age, sex, BMI, ALB, comorbidities, ASA scores, tumor diameter, distance from the anal verge, TNM stage, and neoadjuvant CRT ( Table 2 ).

Operative details are presented in Table 3 . In terms of operative features, there was no statistically significant difference between groups including ligation level of IMA, anastomosis level from the anal verge, extraction site, operative time, intraoperative blood loss, and prophylactic stoma. Eighteen patients underwent surgical plan changes according to ICG evaluation and seven patients according to clinical evaluation (12.5% vs. 4.9%, p = 0.023).

A total of AL was observed in 28 patients: 5 in the ICG group and 23 in the non-ICG group (3.5% vs. 16.1%, p < 0.001, Table 4 ). Among them, 4 (2.8%), 1 (0.7%), and 0 (0%) in the ICG group and 12 (8.4%), 11 (7.0%), and 1 (0.7%) in the non-ICG group were diagnosed with AL of grade A, B, or C (p = 0.040, 0.006, and 1.000, respectively), while 80 (55.9%) in the ICG group and 75 (52.4%) in the non-ICG group underwent neoadjuvant CRT. The ICG group had a less hospital readmission rate than the non-ICG group (0.7% vs. 7.7%, p = 0.003, Table 4 ). Abdominal/pelvic abscess, surgical reinterventions, ileus, bleeding, acute urinary retention, wound infection, postoperative hospital stay, and other complications with a Clavien–Dindo classification score of grade II or higher were similar between the two groups ( Table 4 ). In addition, surgical reintervention with a stoma was required in one patient diagnosed with AL of grade C in the non-ICG group, while the other 27 patients diagnosed with AL of grade A or B were treated conservatively with antibiotics and CT scan drainage (not shown in Table 4 ).

Typical cases: Clinical outcome of transection line modification or not according to anastomotic perfusion score evaluated by ICG or clinical assessment.